1. Field of the Invention
The present invention relates generally to electric power transmission and distribution devices. More particularly, the invention relates to apparatus and methods for protecting a dielectric oil insulating medium used with phase switching equipment, circuit breakers, regulators, phase shifters, tank diverter switches, similar switchgear and capacitor banks for generating, transmitting and/or distributing plural phase electric power.
2. Description of Related Art
Electrical power load control and switching regulation devices for plural phase electric power generation, transmission and distribution devices such as circuit breakers, load regulators, phase shifters, tank diverter switches and similar switch gear, are often immersed in a specially compounded oil having dielectric properties for purposes of insulation, arc isolation and cooling. On occasion, these devices generate extremely high operating temperatures. Although the oil will not burn in the absence of atmosphere or oxygen, small portions will directly decompose under the intense heat of electrical arcing. This is especially true for circuit breakers, regulators and similar switchgear wherein mechanical contact switches are routinely closed and opened with a high potential difference standing at the switch contacts. As mechanical switch contact is closed or opened, brief arcing occurs. Such arcing transforms the oil by decomposition into elemental carbon which remains in the oil as suspended particles of graphite. An accumulation of suspended graphite particles will often reduce the dielectric value and hence, the insulating capacity of the oil.
Under other service circumstances and mechanisms, a dielectric oil system may also accumulate dissolved and entrained water. Water, particulate carbon and other accumulated contaminates in an oil system reduce the dielectric value of the oil and, hence, the effectiveness of the dielectric fluid to protect the internal components of the electrical apparatus.
Fortunately, contaminates such as water and carbon particles may be effectively removed from a system by filtration. Such filtration often takes the form of an external fluid circulation loop that includes a pump, a motor and a canister filter. Conduits channel a circulating flow stream of the dielectric oil between an equipment reservoir in which the electrical equipment is immersed and the filter/pumping equipment. This circulation may be continuous or intermittent.
For plural, two or three phase transmission or distribution of electrical power, each phase is carried on a separate line conduit. Regulating the power, therefore, includes individual capacitors, circuit breakers or regulators respective to each phase of the transmission. Each of these capacitors, circuit breakers or regulators may be physically positioned within a tank that confines an immersion quantity of dielectric fluid. In restatement, there is an insulating oil tank for each phase of the system. A three phase power system, therefore, has three tanks to hold three respective insulating oil reservoirs that immerse three respective switchgear devices.
A respective fluid circulation loop is preferably provided for each tank to maintain the fluid in that tank, exclusively. Hence, for the three switchgear tanks in a three phase power system, there are three respective fluid circulation loops. Each circulation loop includes a separate filter and pump respective to that circulation loop. This separation of fluids is essential to continuing load and equipment analyses of each phase since the accumulation rate and type of contaminates respective to the fluid of each phase is instructive of service needs.
When it is necessary to terminate a fluid circulation loop for one insulating oil tank respective to one power phase, whether automatically or manually, a typical operating procedure may terminate insulating oil circulation about the loops of all tanks. Although termination of all circulation loops in the event of maintenance or repair to one circulation loop is preferable, the procedure is not an absolute necessity. Normally, the circulation pumps respective to each tank in a circulation loop are driven by respective motors and connecting drive lines. Consequently, it is possible to terminate each circulation loop, selectively and individually. However, finding the volumetric space for three pumps and three motors within the permissible confines of a control cabinet becomes a challenge.
It is one objective of the present invention, therefore, to provide a system of separate circulation loops for the insulating oil in each switchgear immersion tank respective to a plural phase electrical power system wherein the circulation of insulating oil in each of the two or more circulation loops is impelled by a respective pump but that all pumps of the several circulation loops are driven by a common drive line that is controlled by a common power source.
Also an objective of the present invention is a unit of three separate pumps respective to each of three dielectric fluid circulation loops wherein all three pumps are driven by the same motor and drive line.